Document a41pZEkEbG1Rp0dGwqQeNqkdR

550 CHAPTER 23 1952 Guide ./ ' U-OTU PER <Ht0(5O rOQ? DEC) Fio. 13. Inside Wall Surface Temperature Cobrechon tor Inside Air Temperatures Other Than 70 F A* -- t -- 70 If At positive: tV -- tw + correction . If At is negative:!' " tw -- correction t* *= inside air temperature (* -- inside wall surface temperature based bn <* -- 70 P tw^ actual tnwito wall surface temperature 2. Calculation of Room Heat Loss The heat transmission coefficients of the-room surfaces are given in fig. 14. They would usually be obtained from Chapter 9. The room heat loss can be calculated in the conventional manner, as outlined in Chapter 11. The calculations are shown in Table 1. The heat loss through the surface areas containing the heating medium is not included in the calculation. The calculated rate of heat loss will determine the amount of heat which must be supplied by the heating panels to the room. WEST Fig. 14. Room Plan for Illustration of Method of Designing a Panel Heating System Data: Values of overall heat transfer coefficients as calculated: .1. Outside walls U =* 0J0 3 Ceiling U -- 0.08 .3. Floor 4 Windows V => 0.36 V -- 0.55 Panel Heating 551 Table 1. Calculated Heat Loss of Room (Fig. 14) Surfaces Area Sq Ft 17 Calculation Ceiling................... - 272 80 352 480 480 0.10 0.55 0.08 _ 272 x 0.10 x 80 80 x 0.55 x 80 No heat loss 480 x 0.08 x 80 Heating panel 3,840 cu ft x 1.50 x 80 x 0.018 Total heat loss......................................... .............................................. Heat Loss Btu/hr 2,176 3,520 0 3,072 0 8,295 17,063 3. Determination of UMRT The calculations for determining UMRT are shown in Table 2. The inside sur face temperatures shown in the fourth column were determined from fig. 12. Table 2. Calculation of UMRT Surface Area Sq Ft Inside Surface* Temperature F* Product (Area x Temperature) Ceiling..................................................... Glass........................................ ............. Total............................................... 0.10 0.08 0.55 272 352 480 80 1,184 65 70 66 43 17,680 24,640 31,680 3,440 77,440 UMRT Total of products __ 77,440 65.4 F Total area 1,184 * Values of Fig. 12. r . wall surface temperature for various U values and outside design temperatures found in 4. Determination of Panel Output Values of total panel output for various panel positions, panel surface tempera' tures and unheated MRT are given in Fig. 11. From Fig. 11> with a floor panel sur face temperature of 85 F and a UMRT of 65.4 F, the total panel output is 34 Btu per (hr) (sq ft of panel surface). Panel area -- 24 x 20 = 480 sq ft -. Panel output = 480 x 34 = 16,320 Btu per hr This panel output of 16,320 Btu per hr is reasonably close to the calculated room loss of 17,063, ana is satisfactory. If this value of total heat output from panel to the room were much less, i.e., 10 or more percent less, than the calculated heat loss from the room, some method of supplementary heating would be needed. Floor panel surface temperatures exceeding 85 F are not recommended. 5. Determination of Panel Input and Water Temperature Fig. 15 presents a graphical method of determining the required water tempera ture and total heat input to a panel for various cover depths, tube or pipe sizes and spacings, and rate of heat output to the room. The panel output for this example has previously been found to be 34 Btu^per (hr) (sq ft). Since some of the heat input to the panel is lost to the ground, it is necessary to supply more than 34 Btu per (hr) (sq ft) to the panel by means of the hot water heating medium. The amount of heat which must be supplied to the panel to give the required output may be determined graphically from Fig. 15. As sume that the panel haa j in. pipes, spaced on 12 in. centers, and that the depth of cover from top of panel surface to top of pipes is 2.5 ini The four sections of Fig.